1. Field of the Invention
The present invention is used in the field of tannery and relates in particular to a device for automatically adjusting the working pressure which can be installed in staking machines with beating plates for stretching and softening industrial hides and similar products.
2. Description of the Prior Art
A conventional staking machine is essentially constituted by one or more pairs of facing plates which can move with respect to each other and have tools which interact alternately with the hides to be treated whilst they are moved substantially at right angles to the reciprocating motion of the plates by virtue of two adjacent conveyor belts.
At least one of the plates is connected, by virtue of a system of the cam-and-linkage type, to a flywheel mass which is rotated by an electric motor so as to promote a periodic motion toward and away from the other plate.
An example of these conventional machines is disclosed in IT-1,247,078, to which reference is made for a detailed description of the various parts, and by the staking machine model PAL-3200 with multiple heads, manufactured by Officine di Cartigliano, S.p.A., assignee of the present application.
In these conventional machines, the tools of one of the mutually opposite plates are generally constituted by projections or pins, whilst those of the other plate are constituted by hollows or similar cavities. The depth of the penetration of the pins in the hollows determines the staking or working "pressure" of the hides.
In order to vary the staking pressure, for example to adapt it to a different kind of hide or treatment, it is necessary to vary the relative position of the plates by making one adjustable in terms of height and angle with respect to the other. For this purpose, the fixed upper plate is peripherally supported by four threaded posts or worm screws which screw into respective complementarily threaded bushes anchored to the frame, so as to move the upper plate toward or away from the bed and therefore toward and away from each other. In order to stably lock the plate once it has been adjusted, there are locking devices constituted by two lateral hydraulic jacks, which act parallel to the axis of the worm screws so as to prevent their rotation within the bushes.
Normally, the worm screws are rotated manually and discontinuously in steps which correspond to translatory motions of approximately 1 mm, using a vernier scale formed on the upper end of the worm screws.
In practice, in order to perform the adjustment it is necessary to perform the following operations: a) stop the conveyor belts of the hides and the motor that drives the flywheel mass until the machine comes to a complete stop; b) depressurize the jacks in order to release the worm screws; c) rotate the worm screws stepwise so as to adjust the height of the fixed plate; d) pressurize the jacks in order to lock the worm screws in the intended position; e) restart the machine and bring it to its normal operating condition. All this entails a considerable waste of time and most of all entails halting work on the machine for a few minutes. If one considers that these operations must sometimes be repeated several times before achieving optimum adjustment, it is evident that they have a considerable negative effect during a day's work and on the entire production cycle, especially for subcontractors and small tanneries.
The disadvantage of being able to perform adjustment discontinuously but not continuously is furthermore evident.
Staking machines are known which have systems for automatically adjusting the staking pressure which however are considerably complicated and require the machine to be designed for this purpose. In other words, with current solutions it is not possible to modify an existing manually-adjusted machine in order to equip it with a continuous and automatic adjustment and avoid stopping it.
An aim of the present invention is to overcome the above drawbacks by providing a device which allows one to automatically adjust, during treatment, the staking pressure in staking machines with beating plates without having to stop the machine.
An object of the present invention is to provide a device which allows a drastic reduction in adjustment times.
A further object is to allow practically continuous staking pressure adjustment or in any case an adjustment which has a very fine resolution.
Still a further object is to provide a device which can be installed on any existing machine of the manually-adjusted type.